I need step by step, what is the common denominator ?

3/2x = 2/5 + 7/10x

To start, you need to find the first smallest term that all the denominators can equal through multiplication. In this specific problem, it is 10x. So you will need to multiply both the numerator and denominator with the number that transforms the denominator
in 10x.

For the first fraction you will need to multiply both numerator and denominator by 5. (3/2x) * (5/5) -> 15/10x.

For the second fraction the number that makes the denominator 10x is 2x. Thus, (2/5) * (2x/2x) -> 4x/10x.

For the third fraction no change is necessary because the denominator is already 10x so that fraction stays the same -> 7/10x

Your resulting equation with a common denominator is:

15/10x = 4x/10x + 7/10x